Adjusting mechanisms for setting the pitch of a variable pitch propeller blade, or a set of such blades, are known in various structural forms. On the one hand, such mechanisms serve to more efficiently utilize the power produced by an engine installed in a watercraft and, on the other hand, they also serve to facilitate maneuvering of the craft. The pitch of the propeller blades can be set manually or automatically as a function of the intended use and it is also possible to set the propeller blades for moving the watercraft backwards, i.e., for running astern.
The variable pitch propeller assembly is rotated by a shaft driven by a motor drive which is commonly housed within the watercraft, but the pitch of the propeller blades is adjusted in a different way. It is known, for example, to introduce a hydraulic fluid into the propeller hub to act on a piston system arranged in the hub so that the propeller blades are adjusted as shown in U.S. Pat. No. 2,931,443.
It is also known to adjust the propeller blades by means of a mechanical linkage or gear with the adjusting force being manually applied. For this purpose, the adjusting movement is transferred to an adjusting member mounted in a non-rotational manner in the propeller hub and the movement is transferred from that member through a thrust bearing to a rotary adjusting member which performs the propeller blade adjustment movement by means of a linkage as shown in U.S. Pat. No. 2,742,097.
Both types of adjusting mechanisms suffer from disadvantages. Thus, the propeller blade adjustment which is accomplished by introducing a pressure medium into the propeller hub is complicated, which means that it is only usable for larger watercraft, and it is also difficult to completely seal the pressure system. The manually actuated adjusting mechanism has the disadvantage that it can only be used in small variable pitch propellers because it is simply not possible to manually apply forces sufficiently large to adjust the propellers in the case of larger propeller assemblies.